Contribute to the development of an animal model of MEN2 in Danio rerio ("zebrafish") to understand the tumor mechanism of MTC and to evaluate the effect of new drugs in the treatment of MTC

• Grant number: 23/03025-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2023
• End date: March 31, 2026
• Field of knowledge: Health Sciences - Medicine - Medical Clinics
• Principal Investigator: Rui Monteiro de Barros Maciel
• Grantee: Isabella Palaver
• Host Institution: Escola Paulista de Medicina (EPM). Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil
• Associated research grant: 21/02752-6 - Multiple Endocrine Neoplasia type 2 (MEN 2) and Medullary Thyroid Carcinoma (TCM): new issues in developmental biology, genetics, immunology, epidemiology, mechanisms of disease and clinical management, AP.TEM

Abstract

MTC in MEN2 shows different behaviors regarding local dependence and the type of RET gene mutation, causing different situations of MTC genesis, disease aggressiveness, and manifestations. Since the discovery of TKs inhibitors, such as vandetanib, cabozantinib, and new drugs, like LOXO-292 and BLU-667, there has been improvement in the treatment of advanced, progressive or symptomatic disease. However, no agent provides complete remission, there are still side effects due to the inhibition of TKs activities in other tissues of the body, and tumors can show distinct responses to these inhibitors. Thus, it is important to use animal models to understand the pathogenesis of MTC and MEN2 and to study new drugs to identify new therapies and control the disease with minimized side effects.The "zebrafish" has been conquering space in studying the mechanisms involved in vertebrate development. This teleost stands out for the series of benefits in its use, specifically:The high fecundity rate, since the female can release from 100 to 200 eggs per matingThe external embryonic development and the transparency of the embryos enable the observation of morphogenetic movements and organogenesis in "real time."The possibility of generating transgenic animals that express the green fluorescent protein (GFP), allowing the monitoring of the tumorigenesis process, the proliferation, and the metastasis, besides the evaluation of the effect of the pharmacological treatment, using high-resolution imagesThe possibility of performing xenotransplants of human tumor cells without the need to repress the immune system of the animal since this system must develop between 48-72 hours after fertilization (hpf)This model enables the in vivo study of the tumor cell invasion process, neovascularization, and angiogenesis, being versatile for studies in oncology since there is a similarity with human histology. In contrast, the zebrafish has 70% of human genes in its orthologue.The animal model, "zebrafish," can express the RET isoforms RET9 and RET51, with the RET9 form identical to humans, while RET51 has 67% homology to humans. Furthermore, the TK domain has the highest degree of conservation, and RET signaling is essential for developing the enteric nervous system in zebrafish, as it is in humans. Moreover, it is essential to note that an advantage of using this animal model to study the ERM is the dispersed anatomical location of the thyroid cells. While in humans, these cells are in the thyroid follicles, in the fish, they are isolated from the thyroid follicles in the ultimobranchial, which are located bilaterally arranged near the cardiac atrium (72 hpf), adjacent to the muscles around the gut (120 hpf), with final positioning in the adult as two clusters of follicles in the transverse septum near the sinus venosus. Using this animal model will allow the study of signaling factors involved in MTC's differentiation, proliferation, and carcinogenesis. Furthermore, it will be possible to investigate how different mutations in the RET domain interfere with aspects of MTC, such as the colonization of new sites, neovascularization, and angiogenesis. Also, it will be possible to study drugs in transgenic animals to identify compounds that modulate cell differentiation and proliferation, allowing the development of new therapies.